What size are the tires on the truck? If you have really tall tires a little more gear.Decide how much high way driving you will be using the truck for and the RPM that you can cruise at with out going crazy. 3.73 is a good place to start your calculations. 62 mph =2700 RPM with 29 inch tall tires,,,62 MPH=3200 RPM with 25 inch tall tires

Well, ideally I would like to run a 23000- 2500 stall and 28-1/2" to 29-1/2" by 10" wide cheaters but my cam wants a 3500+ stall so it sounds like I'll have to change my cam to use the stall and tires I want and keep the truck under 3000rpm at 65mph. The truck probably won't see a lot of highway driving but it will see some, mostly street and strip, so I could handle maybe 3000rpm for an hour if I had to. I like the way my truck drives the way it is, as far as highway rpm's but I'd like more power overall and a tad quicker off the line. I'm trying to find out if I will absolutely have to change my rear gears or if more hp is enough to do the trick so that everything else can stay the same (with the exception of adding posi). I'm just trying to make it as mean of a summertime street machine as I can that will also be fun at the track, not trying to break any records.